This invention relates generally to the manufacture and testing of semiconductor components. More particularly, this invention relates to a test system having an alignment member for aligning semiconductor components to an interconnect of the system.
Due to advances in semiconductor manufacture, singulated semiconductor components, such as packages and dice, are becoming smaller, thinner, and lighter. For example, one type of semiconductor package is referred to as a xe2x80x9cchip scale packagexe2x80x9d because it has a xe2x80x9cfootprintxe2x80x9d (i.e., peripheral outline), and a thickness, that are about the same size as the die contained within the package. As singulated semiconductor components become smaller and lighter, it becomes more difficult to perform test procedures, such as burn-in. Testing of wafer sized components, such as wafers containing dice or chip scale packages, is also more difficult, as the wafers becoming thinner and more densely populated with individual components.
For performing test procedures on semiconductor components, test systems have been developed. The test systems include test circuitry for applying test signals to the integrated circuits contained on the components, and for analyzing the resultant signals. The test systems also include test carriers, or test boards, for retaining the components in electrical communication with the test circuitry. One type of test carrier comprises a temporary package which houses one, or more components, for mounting to a burn-in board. Alternately, test boards can be configured to directly retain multiple components in electrical communication with the test circuitry.
Representative test carriers are described in U.S. Pat. Nos. 5,519,332, 5,541,525, and 5,844,418 to Wood et al., U.S. Pat. No. 5,815,000 to Farnworth et al., and U.S. Pat. No. 5,783,461 to Hembree. A representative test board is described in U.S. Pat. No. 5,578,934 to Wood et al.
The test carriers and test boards include an interconnect for making temporary electrical connections with terminal contacts on the components. The terminal contacts on bare dice typically comprise planar aluminum bond pads, or alternately solder bumps on bond pads. The terminal contacts on chip scale packages typically comprise solder balls, arranged in a dense grid array, such as a ball grid array.
With either bumped or planar terminal contacts, the interconnects can include interconnect contacts, such as metallized recesses, or penetrating projections, that electrically engage the terminal contacts. For example, U.S. Pat. No. 5,592,736 to Akram et al. describes an interconnect with recessed contacts for electrically engaging bumped terminal contacts on unpackaged semiconductor dice. U.S. Pat. No. 5,686,317 to Akram et al. discloses an interconnect with penetrating projection contacts for electrically engaging planar terminal contacts on unpackaged semiconductor dice.
Prior to applying test signals, the components must be aligned with the interconnects, such that the interconnect contacts electrically engage the terminal contacts on the components. One method for aligning the components to the interconnects is with optical alignment techniques. With optical alignment, a viewing device can be configured to simultaneously view the interconnect contacts, and the terminal contacts. The viewing device provides feedback for manipulating vacuum tools for holding and placing the components on the interconnects. For example, an optical alignment system is described in U.S. Pat. Nos. 5,796,264 and 5,634,267 to Farnworth et al.
Although optical alignment techniques are suitable for volume semiconductor manufacture, the optical alignment systems are relatively complex, and are expensive to construct and maintain. For some applications, it may be preferable to employ mechanical alignment techniques. With mechanical alignment, an alignment member of the test system engages and aligns the components to the interconnects.
One type of alignment member includes an alignment opening, configured to engage the peripheral edges of a component. The component can be placed through the alignment opening and guided onto the interconnect. A representative mechanical alignment member is disclosed in U.S. Pat. No. 5,559,444 to Farnworth et al.
As semiconductor components become smaller, and the terminal contacts become more closely spaced, fabricating the alignment members with the required features and dimensional tolerances becomes more difficult. One problem is that the alignment members must be precisely aligned with the interconnects during fabrication of the test system. Misalignment of the alignment member with respect to the interconnect contacts during fabrication of the test system, can adversely affect the temporary electrical connections with the components during test procedures.
The present invention is directed to semiconductor test systems with improved alignment members for aligning the components. This invention also relates to fabrication process for the test systems and alignment members.
In accordance with the present invention, an improved test system for testing semiconductor components, and a method for fabricating the test system, are provided. The test system can be configured to test either singulated or wafer sized components. In either case, the test system includes an interconnect for making electrical connections with the components, and an alignment member for aligning the components to the interconnect. The interconnect includes a pattern of interconnect contacts for making temporary electrical connections with terminal contacts on the components. The alignment member guides the components onto the interconnect, such that the interconnect contacts electrically engage the component contacts.
The interconnect contacts are configured to electrically engage either bumped or planar component contacts. For engaging bumped contacts, the interconnect contacts can comprise metallized recesses, or alternately metallized projections for penetrating the bumped contacts. In addition, the projections can be formed within the recesses such that the bumped contacts are centered by the recesses. For planar contacts, the interconnect contacts can comprise metallized projections configured to penetrate the planar contacts to a self limiting penetration depth.
Several different embodiments of the alignment member are provided. In a first embodiment, a polymer alignment member comprises a curable polymer material formed directly on the interconnect. The polymer alignment member includes a peripheral alignment opening for engaging the peripheral edges of a component under test. The polymer alignment member can also encapsulate and protect wire bonded wires, or other electrical paths, to the interconnect.
A method for fabricating the polymer alignment member includes the steps of: forming a mold on the interconnect, depositing a curable polymer in viscous form on the interconnect and mold, curing the polymer, and then removing the mold. Alternately, a photoimageable material, such as a thick film resist, can be deposited on the interconnect, photo-patterned, developed to form the alignment openings, and then cured. Optionally, the polymer alignment member can also include a pattern of fine alignment openings configured to center the component contacts with respect to the interconnect contacts to provide fine alignment.
In a second embodiment, the interconnect includes an etched alignment member formed integrally with a substrate of the interconnect. In this embodiment, the interconnect substrate comprises an etchable material, such as silicon or ceramic, and the alignment member comprises a pocket etched part way through the substrate. The pocket has a peripheral shape that matches a peripheral outline of the component, and a sloped sidewall for engaging an edge of the component. In addition, the pocket includes a planar surface on which the interconnect contacts are located. As with the previous embodiment, the interconnect contacts can comprise metallized recesses, or metallized projections for penetrating the component contacts. The projections can also be placed within recesses, such that the recesses center the component contacts onto the projections. One advantage of this embodiment is that alignment of the alignment member and interconnect contacts is performed using semiconductor fabrication techniques, such as masking and etching, and is therefore xe2x80x9cfabxe2x80x9d aligned.
A method for fabricating the etched alignment member includes the steps of: providing a substrate, etching a pocket in the substrate comprising a sidewall for engaging an edge of the component and a planar surface, forming interconnect contacts on the planar surface within the pocket, and then forming conductive vias in the substrate to the interconnect contacts.
In a third embodiment, an alignment member comprises a separate member that is attached to the interconnect. For attaching the separate alignment member to the interconnect, an alignment fixture is provided. The alignment fixture has a peripheral outline and thickness that are identical to the components being tested. In addition the alignment fixture includes alignment features such as holes, alignment marks, grooves or alignment fiducials, that allow precise alignment to the interconnect. With the alignment fixture simulating the component and aligned with the interconnect, the separate alignment member can be aligned with the alignment fixture and attached to the interconnect. The alignment fixture is then removed to allow performing of the test procedures.
Also with the separate alignment member bond wires to the interconnect can be encapsulated in a curable polymer. In addition, the interconnect can include dummy bond wires, and dams, which prevent the encapsulant from flowing onto the interconnect contacts, and onto the area occupied by the alignment member.
In a fourth embodiment the test system includes an assembly fixture for aligning the interconnect during assembly of the test system.
In a fifth embodiment the alignment member comprises a separate member configured to align the component and to provide bond wire protection.